章节大纲

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    Like Pushing a Humvee Uphill
    ::就像推着一辆悍马车上山

    You can tell by their faces that these airmen are expending a lot of energy trying to push this Humvee up a slope. The men are participating in a that tests their brute strength against that of other teams. The Humvee weighs about 13 thousand pounds, so it takes every ounce of energy they can muster to move it uphill against the force of gravity. Transport of some substances across a plasma membrane is a little like pushing a Humvee uphill — it can't be done without adding energy.
    ::你可以从他们的脸上看出,这些飞行员正在花费大量精力,试图把这辆悍马推上一个斜坡。这些男子正在参加一个比其他队的强力测试他们的野蛮力量。悍马的重量约为13,000磅,因此他们能调动的能量就用每一盎司的力量把它推上山来对抗引力。将一些物质运过等离子膜有点像把悍马推上山——如果不增加能量,这是不可能做到的。

    What Is Active Transport?
    ::什么是“主动运输”?

    Some substances can pass into or out of a across the plasma membrane without any energy required because they are moving from an area of higher concentration to an area of lower concentration. This type of transport is called . Other substances require energy to cross a plasma membrane, often because they are moving from an area of lower concentration to an area of higher concentration. This type of transport is called active transport . The energy for active transport comes from the energy-carrying molecule called ATP (adenosine triphosphate). Active transport may also require called pumps,  which are embedded in the plasma membrane. Two types of active transport are membrane pumps (such as the  sodium-potassium pump) and vesicle transport .
    ::某些物质可以穿过等离子膜进入或流出等离子膜,而不需要任何能量,因为它们正在从高浓度地区转移到低浓度地区。这种运输称为“运输”。其他物质需要能量才能穿过等离子膜,常常因为它们从低浓度地区转移到高浓度地区。这种运输称为“主动运输”。活性运输的能量来自称为ATP(乙酸三磷酸)的含有能量的分子。主动运输也可能需要所谓的水泵,这些水泵嵌入等离子膜。两种有效的运输是膜泵(例如钠-钾泵)和输卵器运输。

    The Sodium-Potassium Pump
    ::钠-钚泵

    The is a mechanism of active transport that moves sodium ions out of the cell and potassium ions into the cells  —  in all the trillions of cells in the body! B oth ions are moved from areas of lower to higher concentration, so energy is needed for this "uphill" process. The energy is provided by ATP. The sodium-potassium pump also requires  carrier proteins . Carrier proteins bind with specific ions or molecules, and in doing so, they change shape. As carrier proteins change shape, they carry the ions or molecules across the membrane. T he figure shows in greater detail how the sodium-potassium pump works, as well as the specific roles played by carrier proteins in this process.
    ::这是一种将钠离子从细胞和钾离子转移到细胞的活性迁移机制—— 在身体的所有数万亿个细胞中! 两种离子都从低浓度地区移到高浓度地区, 因此这种“ 上坡” 过程需要能量。 由 ATP 提供能量。 钠- 钾泵也需要携带蛋白质。 载体蛋白与特定的离子或分子结合, 并随之改变形状。 随着载体蛋白变形, 它们携带离子或分子横跨膜。 该图更详细地显示了钠- 泵是如何工作的, 以及载体蛋白在这一过程中的具体作用 。

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    The sodium-potassium pump. The sodium-potassium pump moves sodium ions (Na+) out of the cell and potassium ions (K+) into the cell. First, three sodium ions bind with a carrier protein in the cell membrane. Then, the carrier protein receives a phosphate group from ATP. When ATP loses a phosphate group, energy is released. The carrier protein changes shape, and as it does, it pumps the three sodium ions out of the cell. At that point, two potassium ions bind to the carrier protein. The process is reversed, and the potassium ions are pumped into the cell.
    ::钠-钾泵:钠-钾泵将钠离子(Na+)从细胞和钾离子(K+)移出细胞;首先,三种钠离子与细胞膜中的载体蛋白结合;然后,载体蛋白从ATP获得一组磷酸盐;当ATP失去一个磷酸盐组时,释放能量;承体蛋白质改变形状,并按其做法,将3个钠离子抽出细胞;到那时,2个钾离子与载体蛋白结合;这一过程被逆转,钾离子被抽进细胞。

    To appreciate the importance of the sodium-potassium pump, you need to know more about the roles of sodium and potassium in the body. Both are essential dietary minerals . You need  to get  them from the foods you eat. Both sodium and potassium are also electrolytes, which means  they dissociate into ions (charged particles) in solution, allowing them to conduct electricity. Normal body functions require a very narrow range of concentrations of sodium and potassium ions in body fluids, both inside and outside of cells.
    ::为了了解钠-钾泵的重要性, 您需要了解更多关于钠和钾在体内作用的信息。 钠和钾都是必需的饮食矿物。 您需要从食物中获取它们。 钠和钾也是电解液, 这意味着它们分离成溶解的离子( 充电颗粒) , 从而可以进行电力操作。 正常身体功能需要细胞内外的体液中钠和钾离子浓度非常窄。

    • Sodium is the principal ion in the fluid outside of cells. Normal sodium concentrations are about ten times higher outside of cells than inside of cells.
      ::钠是细胞外液体中的主要离子,正常钠浓度比细胞内大约高出十倍。
    • Potassium is the principal ion in the fluid inside of cells. Normal potassium concentrations are about 30 times higher inside of cells than outside of cells.
      ::钾是细胞内液体中的主要离子,细胞内普通钾浓度比细胞外大约高出30倍。

    These differences in concentration create an electrical and chemical gradient across the , called the membrane potential . Tightly controlling the membrane potential is critical for vital body functions, including the transmission of and contraction of . A large percentage of the body's energy goes to maintaining this potential across the membranes of its trillions of cells with the sodium-potassium pump.
    ::浓度的这些差异造成了整个细胞的电气和化学梯度,称为膜潜力。严格控制膜潜力对于包括输电和收缩在内的重要身体功能至关重要。 人体能量的很大一部分用于保持其用钠-钾泵隔着数万亿个细胞膜的这种潜力。

    Vesicle Transport
    ::车辆运输

    Some molecules, such as proteins, are too large to pass through the plasma membrane, regardless of their concentration inside and outside the cell. Very large molecules cross the plasma membrane with a different sort of help, called vesicle transport . Vesicle transport requires energy input from the cell, so it is also a form of active transport. There are two types of vesicle transport: endocytosis and exocytosis . Both types are shown in the figure .
    ::有些分子,例如蛋白质,体积太大,无法通过等离子膜,不管其细胞内外的浓度如何。非常大的分子通过等离子膜,有不同种类的帮助,称为输卵器运输。输卵器运输需要细胞的能量输入,因此也是一种活性运输形式。有两种类型的输卵器运输:内分泌和排入。两种类型都显示在图中。

    Endocytosis
    ::内分泌病

    Endocytosis is a type of vesicle transport that moves a substance into the cell. The plasma membrane completely engulfs the substance, a vesicle pinches off from the membrane, and the vesicle carries the substance into the cell. When an entire cell or other solid particle is engulfed, the process is called phagocytosis . When fluid is engulfed, the process is called pinocytosis .
    ::内分泌中毒是一种将物质移入细胞的输卵管迁移方式。等离子膜完全吞没了该物质,一种从膜中抽取的输卵管,而输卵管将该物质带入细胞。当整个细胞或其他固态粒子被吞没时,这一过程被称为发细胞。当液体被吞没时,这一过程被称为皮诺细胞病。

    Exocytosis
    ::血孔病

    Exocytosis is a type of vesicle transport that moves a substance out of the cell. A vesicle containing the substance moves through the cytoplasm to the cell membrane.  Because the vesicle membrane  is a like the plasma membrane , the vesicle membrane fuses with the cell membrane, and the substance is released outside the cell.
    ::蛋白质解剖是一种将物质从细胞中移出的一种输卵管运输方式。含有该物质的卵囊通过细胞顶板移动到细胞膜。由于卵囊膜与血浆膜相似,因此与细胞膜结合的卵囊膜与细胞膜结合,并且该物质在细胞外释放。

     

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    Illustration of the two types of vesicle transport, exocytosis and endocytosis
    ::两种输卵器运输、排出性硬化和内分泌性硬化的说明

    Feature: My Human Body 
    ::特质:我的人体

    Maintaining the proper balance of sodium and potassium in body fluids by active transport is necessary for life itself, so it's no surprise that getting the right balance of sodium and potassium in the diet is important for good health. Imbalances may increase the risk of high , heart disease, , and other disorders. 
    ::通过活性运输在体液中保持钠和钾的适当平衡对于生命本身是必要的,因此,在饮食中取得钠和钾的适当平衡对于健康非常重要并不奇怪。 不平衡可能会增加高发、心脏病和其他疾病的风险。

    If you are like the majority of Americans, sodium and potassium are out of balance in your diet. You are likely to consume too much sodium and too little potassium. Follow these guidelines to help ensure that these minerals are balanced  in the foods you eat:
    ::如果你像大多数美国人一样, 钠和钾在饮食上是不平衡的。 你可能会消费过多的钠和太少的钾。 遵守这些指导方针有助于确保这些矿物质在食物中保持平衡。 :

    • Total sodium intake should be less than 2300 mg/day. Most salt in the diet is found in processed foods, or added with a salt shaker. Stop adding salt and start checking food labels for sodium content. Foods considered low in sodium have less than 140 mg/serving (or 5 percent daily value).
      ::钠总摄入量应低于每天2,300毫克/日,饮食中的大部分盐在加工食品中找到,或添加盐搅拌器;停止加盐,开始检查钠含量的食品标签;钠低的食物低于140毫克/日(即每日价值5%)。
    • Total potassium intake should be 4700 mg/day. It's easy to add potassium to the diet by choosing the right foods — and there are plenty of choices! Most fruits and vegetables are high in potassium. Potatoes, bananas, oranges, apricots, plums, leafy greens, tomatoes, lima beans, and avocado are especially good sources. Other foods with substantial amounts of potassium are , meat, poultry, and whole grains.
      ::钾总摄入量应为4700毫克/天。通过选择正确的食物,很容易在饮食中添加钾——而且有很多选择!大多数水果和蔬菜在钾中含量很高。马铃薯、香蕉、橘子、杏子、李子、叶绿、西红柿、豆豆和鳄梨是特别好的来源。其他含有大量钾的食物包括肉类、家禽和整粒谷物。

    Summary
    ::摘要

    • Active transport requires energy to move substances across a plasma membrane, often because the substances are moving from an area of lower concentration to an area of higher concentration, or because of their large size. Two types of active transport are membrane pumps (such as the sodium-potassium pump) and vesicle transport.
      ::活性运输需要能量将物质通过等离子膜移动,这往往是因为这些物质正在从低浓度地区转移到高浓度地区,或者由于其体积大,两种活性运输是膜泵(例如钠-钾泵)和输卵管运输。
    • The sodium-potassium pump is a mechanism of active transport that moves sodium ions out of the cell and potassium ions into the cell, both against a concentration gradient, in order to maintain the proper concentrations of ions both inside and outside the cell, and to thereby control membrane potential.
      ::钠-钾泵是一种活性迁移机制,将钠离子从细胞中移出,并将钾离子移入细胞中,两者均针对浓度梯度,以便保持细胞内外离子的适当浓度,从而控制膜潜力。
    • Vesicle transport is a type of active transport that uses vesicles to move large molecules into or out of cells.
      ::输卵器运输是一种使用输卵器将大分子运入或运出细胞的一种活性运输方式。

    Review
    ::回顾

    1. Define active transport.
    ::1. 界定主动运输。

    2. What is the sodium-potassium pump? Why is it so important?
    ::2. 钠-钾泵是什么?为什么如此重要?

    3. Name two types of vesicle transport. Which type moves substances out of the cell?
    ::3. 列出两种输卵器运输方式:哪种类型的物质将物质从细胞中移出?

    4. T he drawing below shows the fluid inside and outside of a cell. The dots represent molecules of a substance needed by the cell. Explain which type of transport — active or passive — is needed to move the molecules into the cell. 
    ::4. 下面的图示显示了细胞内外的液体,点表示细胞需要的物质分子,请解释需要哪种运输方式——主动或被动——才能将分子移入细胞。

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    5. What are the similarities and differences between phagocytosis and pinocytosis?
    ::5. 地细胞病和皮质细胞病之间有什么相似之处和不同之处?

    6. The sodium-potassium pump is a:
    ::6. 钠-钾泵是:

    a. phospholipid
    ::a. 磷素

    b. protein
    ::b. 蛋白质

    c. carbohydrate
    ::c. 碳水化合物

    d. ion
    ::d. 离子

    7. What is the functional significance of the shape change of the carrier protein in the sodium-potassium pump after the sodium ions bind?
    ::7. 钠离子结合后钠-钾泵中载体蛋白的形状变化的功能意义是什么?

    8. A potentially deadly poison derived from plants called ouabain blocks the sodium-potassium pump and prevents it from working. What do you think this does to the sodium and potassium balance in cells? Explain your answer.
    ::8. 一种可能致命的毒药,来自称为 " 乌巴因 " 的植物,它阻断了钠-钾泵,使其无法起作用。你认为这对细胞中的钠和钾平衡有何影响?请解释你的答复。

    9. True or False:  The sodium-potassium pump uses one protein to pump both sodium and potassium.
    ::9. 真实或假:钠-钾泵使用一种蛋白质泵钠和钾。

    10. True or False:  Vesicles are made of nuclear membrane.
    ::10. 真实或假:卵子由核膜制成。

    11. An electrical gradient across the cell membrane is called a __________  ___________.
    ::11. 跨细胞膜的电梯度称为 。

    12. Chemical signaling molecules called neurotransmitters are released from nerve cells (neurons) through vesicles. This is an example of:
    ::12. 被称为神经传递器的化学信号分子从神经细胞(中子)通过输卵管释放出来。

    a. pinocytosis
    ::a. 皮环球细胞病

    b. phagocytosis
    ::b. 发细胞病

    c. endocytosis
    ::c. 内分泌疾病

    d. exocytosis
    ::d. 排球病

    13. The energy for active transport comes from
    ::13. 活性运输的能源来源于:

    a. ATP
    ::a. ATP

    b. RNA
    ::b. RNA

    c. carrier proteins
    ::c. 载体蛋白质

    d. sodium ions
    ::d. 钠离子

    14. Transport proteins that move substances into and out of a cell are located in the ___________ __________ .
    ::14. 将物质运入和运出细胞的运输蛋白质位于________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

    Explore More
    ::探索更多

    The video below demonstrates phagocytosis. 
    ::下面的录像显示的是脑细胞病。